It is known that people utilize more and more wireless portable devices; therefore, many of these devices configured with dual-band antennas appear on the market for people to choose from.
In order to carry around easily, these devices are usually designed small in physical size. The small physical size limits the shapes of dual-band antennas so that the antennas for portable electronic devices need to compromise between function and physical size. FIG. 1 shows a dual-band antenna of the prior art with a first receiving input 101 and a second receiving input 103. Both of them have a long strip shape structure whose length corresponds to receiving frequencies. The portable electronic device receives signals through a feed point 105. The antenna of the prior art is designed flat to fit into the limited space; however, such design might influence receiving efficiency.